Modern electronic devices typically include a plurality of integrated circuit (IC) or semiconductor chips that communicate with each other. Wireless communication devices, such as Wi-Fi and Bluetooth enabled devices, include transmitter and receiver circuits that exchange data between each other using radio frequency (RF) signals. Typically, the power level of RF signals output by the transmitter circuits are specified to meet various standards (e.g., set forth by the FCC, the IEEE, and others) and/or to meet customer specifications. As known in the art, transistor operating characteristics vary with temperature, and thus the power level of signals output by the transmitter circuits also varies with temperature. Indeed, changes in the operating temperature of such wireless communication devices may result in output power levels that do not meet the specified power levels, and may also result in data distortion and/or data loss.
To compensate for changes in operating temperature, a look-up table provided within each of a plurality of similar wireless communication devices can be used to maintain the power of the device's output signal at a constant level in response to temperature changes. More specifically, the look-up table provided within each wireless communication device stores a plurality of predetermined power correction values for a corresponding plurality of temperatures, and if the temperature changes during normal operation of the device, the look-up table provides a corresponding power correction value to the device's transmitter circuit, which in response thereto adjusts the power level of the output signal to compensate for the temperature change.
The predetermined power correction values are typically generated by selecting one of a plurality of the devices for testing prior to delivery to customers, measuring the output power level of the selected test device for a variety of different temperatures, and then determining a desired power setting level and an associated correction value for each of the different temperatures. Then, the same set of correction values is programmed into the look-up table within each of the devices prior to their delivery to customers. In this manner, all like devices (e.g., all devices belonging to a particular product family) have identical power correction values programmed therein, and thus should all behave identically over various operating temperature ranges.
However, because of process variations inherent in the fabrication of semiconductor devices, devices of the same design (e.g., having identical transistor layouts) typically have varying operating characteristics. For example, although transistor size may be precisely controlled, imperfections in available doping technologies typically result in transistors of the same design behaving differently, and therefore devices fabricated from different wafers (or even from different portions of the same wafer) usually have different operating characteristics. Thus, although a plurality of IC devices can be designed and fabricated to have the same specified operating characteristics, these devices inevitably operate differently from one another, especially during variations in operating temperatures. Accordingly, the predetermined power correction values derived from the selected test device and then stored in each device's look-up table provides only an approximation of how the output power of each device will change in response to temperature fluctuations, and therefore do not ensure that every device will meet its specified operating characteristics in response to temperature variations.
One solution is to individually test each device to calculate power correction values specific to that device before the device is delivered to customers. Unfortunately, measuring the output signal power for each and every device for a variety of different temperatures would be time-consuming, labor-intensive, and expensive, and is therefore not practical for large-scale production of a semiconductor product. Thus, what is needed is an improved method for maintaining the output power of wireless communication devices at a constant level despite variations in operating temperatures.